The present invention relates to reproduction apparatus. More specifically, the invention relates to copiers having duplexing capabilities, and to document feeders that circulate original document sheets automatically, for producing duplex or simplex collated copies in page-sequential order without a sorter.
It is well known in the prior art to provide copiers with duplexing capabilities, with document feeders that circulate the original in a manner suitable for producing collated copies, or with document inverters that present both faces of the document for copying. Examples include: (1) in relation to the first feature--U.S. Pat. Nos. 3,318,212; 3,536,398; 3,548,783; 3,615,129; 3,630,607; 3,645,615; 3,671,118; 3,672,765; 3,687,541; 3,697,171; 3,775,102; 3,844,654; 3,856,295; 3,862,802; 3,866,904; 3,869,202; 3,947,270, and Research Disclosure Publication No. 14237, Vol. 142, Feb. 1976 (available from Industrial Opportunities Ltd., Homewell, Havant, Hampshire, P.O. 9-1EF, United Kingdom; (2) in relation to the second feature--U.S. Pat. Nos. Re. 27,976; 3,552,739; 3,556,511; and 3,709,595; (3) and, in relation to the third feature U.S. Pat. Nos. 3,227,444; 3,416,791 and 3,675,999.
It is also known in the prior art to combine certain of the above mentioned features in a unified structure or control. U.S. Pat. No. 3,630,607 discloses a collating feeder on a copier having duplex capabilities. U.S. Pat. No. 3,844,653 discloses a copier having duplex capabilities with a document inverting mechanism. U.S. Pat. No. 3,862,802 discloses a duplex copier with a document inverting mechanism, and is said to be useable with a sorter to produce collated copies. Research Disclosure, Vol. 133, No. 13329, May 1975 discloses a manual approach for producing collated duplex copies without a sorter.
The cross-referenced patent applications Ser. Nos. 691,937 and 867,842 present further improvements in copy and document handling. Both relate to apparatus for yielding duplex or two-sided copies in a fully automatic manner, and for producing collated copies without the burden of a sorter. Both also include recirculating, inverting document feeders and duplexing copy processors that are particularly conducive to simplified finishing operations. Application Ser. No. 867,842 discloses apparatus for producing copies in page-sequential order, thus enhancing still further the convenience and efficiency of copying.
The above-mentioned patents and applications disclose an impressive number of features for supplementing the basic copying function to facilitate the total copying operation. Certain disadvantages remain, however, and it is to the alleviation of these disadvantages that the present invention is directed. In some cases, for example, prior approaches include two document hoppers and a document preparation step. While satisfactory for their intended purposes, the two hopper approaches suffer from the disadvantages of multiple feeders, extended guide channels and undesirable document preparation steps. In addition, and referring now to copy handling aspects, prior approaches suggest a "double pass" approach, where the copy sheets are transported along a somewhat tortuous path through the fuser and back to the photoconductor between the transferring of images to opposite faces of the sheets. With such approaches, the intermediate fusing operation adversely effects the condition of copy sheets and can complicate copy handling. Still another problem relates to relatively long copy-sheet paths. When short documents of two or three pages are copied, for example, it may take longer for the first copy sheet to return the second time to the photoconductor than to present all of the other copy-sheets the first time. This reduces the ability of the copier to handle some jobs efficiently.